1. Field of the Invention
This invention relates generally to the compression of gaseous matter and relates particularly to a rotary compressor having a rotor with a plurality of sliding blades mounted within a housing, as well as means for increasing the efficiency of such compressor.
2. Description of the Prior Art
Heretofore many efforts have been made to provide blade-type rotary compressors which include a housing having an elongated generally cylindrical bore with a rotor eccentrically mounted therein. Such rotor usually has a plurality of blades or sliding vanes disposed within grooves or recesses generally radially of the rotor so that when the rotor is rotated the blades slide in and out of the grooves to define a plurality of compression pockets whose volume constantly changes as the rotor rotates. The housing normally is provided with a suction opening on one side through which gaseous matter is introduced into the bore of the housing so that the gaseous matter enters the compression pockets as the pockets are enlarging until the pockets reach maximum capacity. Thereafter, the introduction of gaseous matter is interrupted and the trapped gaseous matter is compressed and discharged through a pressure discharge opening in the housing.
In order to permit the blades or sliding vanes to rotate against the fixed housing, a film of oil is injected into the housing along the length of the bore for cooling and lubricating purposes. However, sealing the ends of the rotor and the blades or sliding vanes has presented particular problems since the ends of the rotor and blades are not only rotating relative to the fixed end caps of the housing, but the blades are simultaneously moving in and out radially of the rotor. Additionally problems have been encountered when the compressor was being started since non-compressible cooling and lubricating oil has had an opportunity to collect within the compression pockets and a substantial amount of work has been required to compress the gaseous matter trapped in the compression pockets.
Accordingly a drive motor which was substantially larger than required during running has been required in order to start the rotor and get the rotor to operating speeds. After the rotor is rotating at operating speed, such rotor functions as a fly wheel so that substantially less power is required to keep the rotor operating. Also the trapped non-compressible oil, as well as the gaseous matter within the compression pockets have caused damage to the compressor and particularly the blades or sliding vanes during the starting operation of the compressor.
Some efforts have been made to provide a capacity control for rotary compressors, such as the Tosh U.S. Pat. No. 3,451,614; however, these prior art devices normally have been located in one end only of the compressor and have provided a partial bypass only and have not provided full unloading for starting the compressor. Additionally some efforts have been made to inject oil under pressure into the area adjacent to the ends of the rotor to provide an oil sealed interface; however, the end seals have continued to present a major problem to rotary compressors. Laboratory tests indicated that leakage at the interface between the end of the rotor and the housing included 50 to 75% of total compressor capacity loss.
Some additional examples of the prior art include the U.S. Pat. Nos. to Pfeiffer 1,890,003; Dubrovin 2,337,849; Godbe 2,445,573; Menon 2,969,021; Hart 3,016,184; Keller 3,797,975 and British Pat. No. 704,110.